使用ASIHttpRequest的setCompletionBlock、setFailedBlock时碰到一些诡异的内存泄漏和莫名其妙的行为(如:无法release对象)。
1. 声明ASIHttpRequest时一定要使用__block关键字
__block关键字告诉block不要retain request,这对于防止循环retain非常重要!!因为request总是会retain block
2. 谨慎处理block与对象的关系
当setCompletionBlock/setFailedBlock内部使用对象的instance var时,self会被retain(If you access an instance variable by reference, self is retained;)。所以在request结束前向对象发送release消息不会导致对象的释放(dealloc),亦即:该对象依然可进行所有操作,这将导致诸多你意想不到的结果。
3. 解决第2点的问题
3.1 仔细拿捏block与对象的关系 + 按值的方式访问instance var(If you access an instance variable by value, the variable is retained.)
3.2 不使用block,而使用ASIHttpRequestDelegate
4. 参考资料
4.1 http://allseeing-i.com/ASIHTTPRequest/How-to-use - Using blocks
4.2 Blocks Programming Topics - Object and Block Variables
接口部分:
//
// LYHASIRequestBlock.h
// ASIBlockTest
//
// Created by Charles Leo on 14-7-23.
// Copyright (c) 2014年 Charles Leo. All rights reserved.
//
#import <Foundation/Foundation.h>
#import "ASIHTTPRequest.h"
#import "ASIFormDataRequest.h"
typedef void (^RequestBlock) (void);
@interface LYHASIRequestBlock : NSObject <ASIHTTPRequestDelegate>
{
ASIHTTPRequest * getRequest;
ASIFormDataRequest * postRequest;
NSURL * url;
RequestBlock finishBlock;
RequestBlock failBlock;
RequestBlock startBlock;
NSString * requestType;
}
//接收到的数据
@property (strong,nonatomic) NSData * receiveData;
//请求完成的block
- (void)didFinishBlock:(RequestBlock)block;
//请求失败的block
- (void)didFailedBlock:(RequestBlock)block;
//请求开始的block
- (void)didStartBlock:(RequestBlock)block;
//取消请求
- (void)cancelRequst;
//get请求方法
- (void)getRequest:(NSString *)getUrl;
//post请求方法
- (void)postRequest:(NSString *)postUrl andKeys:(NSArray *)keyArray andValues:(NSArray *)valueArray;
@end
实现部分:
//
// LYHASIRequestBlock.m
// ASIBlockTest
//
// Created by Charles Leo on 14-7-23.
// Copyright (c) 2014年 Charles Leo. All rights reserved.
//
#import "LYHASIRequestBlock.h"
@implementation LYHASIRequestBlock
- (void)getRequest:(NSString *)getUrl
{
requestType = @"GET";
getRequest = [[ASIHTTPRequest alloc]initWithURL:[NSURL URLWithString:getUrl]];
getRequest.delegate = self;
getRequest.timeOutSeconds = 15;
[getRequest startAsynchronous];
}
#pragma mark -GET请求的代理方法
//开始请求
- (void)requestStarted:(ASIHTTPRequest *)request
{
startBlock();
}
//请求完成
- (void)requestFinished:(ASIHTTPRequest *)request
{
self.receiveData = request.responseData;
finishBlock();
}
//请求失败
- (void)requestFailed:(ASIHTTPRequest *)request
{
failBlock();
}
//post请求
-(void)postRequest:(NSString *)postUrl andKeys:(NSArray *)keyArray andValues:(NSArray *)valueArray
{
postRequest = [[ASIFormDataRequest alloc]initWithURL:[NSURL URLWithString:postUrl]];
postRequest.timeOutSeconds = 15;
postRequest.delegate = self;
for (int i = 0; i<keyArray.count; i++) {
[postRequest setPostValue:[valueArray objectAtIndex:i] forKey:[keyArray objectAtIndex:i]];
}
[postRequest setDidFinishSelector:@selector(didFinishPostRequest:)];
[postRequest setDidStartSelector:@selector(didStartPostRequest:)];
[postRequest setDidFailSelector:@selector(didFailPostRequest:)];
[postRequest startAsynchronous];
}
#pragma mark - POST请求的代理方法
//请求开始
- (void)didStartPostRequest:(ASIFormDataRequest *)request
{
startBlock();
}
//请求完成
- (void)didFinishPostRequest:(ASIFormDataRequest *)request
{
finishBlock();
}
//请求失败
- (void)didFailPostRequest:(ASIFormDataRequest *)request
{
failBlock();
}
//设置Blocks
//设置开始块
- (void)didStartBlock:(RequestBlock)block
{
[startBlock release];
startBlock = [block copy];
}
//设置完成块
-(void)didFinishBlock:(RequestBlock)block
{
[finishBlock release];
finishBlock = [block copy];
}
//设置失败块
-(void)didFailedBlock:(RequestBlock)block
{
[failBlock release];
failBlock = [block copy];
}
//取消请求
- (void)cancelRequst{
if ([requestType isEqualToString:@"GET"])
{
[getRequest cancel];
}
else if([requestType isEqualToString:@"POST"])
{
[postRequest cancel];
}
}
-(void)dealloc
{
[getRequest release];
[postRequest release];
[startBlock release];
[finishBlock release];
[failBlock release];
[super dealloc];
}
@end
参考:http://www.cocoachina.com/bbs/read.php?tid=95100
http://code4app.com/snippets/one/%E7%94%A8Block%E5%B0%81%E8%A3%85ASIHttpRequest/5428f5b8933bf0bf118b51d8
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